Leishmania mexicana mexicana glucose-6-phosphate isomerase: crystallization, molecular-replacement solution and inhibition.

Glucose-6-phosphate isomerase (PGI; EC 5.3.1.9; also often called by its old nomenclature phosphoglucose isomerase) is an intracellular enzyme that catalyses the reversible conversion of D-glucose 6-phosphate (G6P) to D-fructose 6-phosphate (F6P). The native Leishmania PGI is a homodimeric molecule of 60 kDa per monomer with 47% sequence identity to human PGI. It has been shown to be present in both the cytosol and the glycosome of Leishmania promastigotes and represents a potential target for rational drug design. The present work describes the crystallization of two bacterially expressed Leishmania PGI constructs, one corresponding to the natural protein and the other to an N-terminally deleted form. Crystals of both forms are identical and present a large c unit-cell parameter. A complete data set was collected from the N-terminally deleted PGI to a resolution of 3.3 A in space group P6(1), with unit-cell parameters a = b = 87.0, c = 354.7 A, alpha = beta = 90, gamma = 120 degrees. A preliminary study of the first inhibitors to be evaluated on the Leishmania enzyme is also reported.